This paper offers a simple way to assessthe impact on the economy of Nigeria of an economicpartnership agreement (EPA) between the ECOWAS countries andthe European Union (EU) , based on the market access offercontained in the negotiation proposals in early 2014 withthe following key elements: liberalization, to the benefitof the EU, of West African market access for 75 percent oftariff lines over a period of 20 years; three categories ofproducts subject to gradual liberalization, in four stagesof five years each, starting on December 31, 2019 for thefirst category being liberalized and finishing in 2035 forthe third category. The fourth category of products,representing one quarter of all tariff lines, is not subjectto liberalization; and possibility of recourse to tradedefense measures, including bilateral safeguard measures(article 22) and an infant industry clause (article 23). Theanalysis presented in this paper is based on a newmethodology that combines the advantages of a partialequilibrium modeling framework with the wealth of firm levelinformation contained in a World Bank enterprise survey forNigeria. The intention is to add value to the policy debatearound the EPA by generating results that are intuitive andtransparent to a non-technical audience, and that rely on alimited number of simple assumptions, while adding precisionand detail to the expected impact on the domestic economy.